P0088 questions

[tr4dude]

ok, i rebuilt my engine, new rings, recoated pistons, all internals were checked and renewed as needed. reused 4 injectors the fifth would not come out so i rebuilt another head of another core.

tested leakoff with cold engine, after 2 ten seconds of cranking here are the results, does this need to be tested with the engine hot? excuse the dirty number one injector it came from another running truck and was the only loose injector after cleaning some black death from the other ones.



after starting the fuel rail pressure goes to 7000, i checked low pressure pump and it is giving 65 psi static pressure and 7/8 gallon flow in 51 seconds, 70 psi steady while running.

engine starts and promptly but upon reving it i get code P0088, I notice a change in engine tone after about 15 seconds after startup with it idling.

I changed the fuel rail and injector pump from a running engine and nothing changed.

I also notice that it sounded like one cylinder fired a couple times with the cam sensor unplugged during the leak off test.

Could my fault be in and injector being stuck open due to contamination or wear, what would be the best way to test them without going to the dealer?

[tr4dude]

Did some more testing this weekend.

took all the injectors out and hooked them up to the fuel rail and had them pointing towards the driver side fenderwell. Used jumperlines to the injector from the plug and had an assistant crank the engine will i stood a few feet away. thanks to user bramage for this insightfull procedure, all the injectors sprayed ok but #4 had small amount of fuel leaking from the tip after it sprayed while the other four had none.

I dont recommend this procedure but if you use it STAND SEVERAL FEET AWAY!!!! high pressure fuel will KILL you if it penetrates your skin.

I think after it started and ran, the injector is sticking causing the change in engine sound and raising the fuel rail pressure.

Will this cause the fuel rail pressure to spike by making the ecu compensate for the leakoff in the tip of the injector or the injector sticking?

I did subject this particular injector to some localized heat to remove it from the head during teardown. big no no i quess.

I will get a new injector in the next day or two and see if that will put the nail in the coffin for this hiccup. and will replace the rest of them as money allows!

[Aqua Puttana]

Since nobody else has replied yet...

Your approach sounds logical to me. If you have 4 injectors behaving one way and another different (your observed "drip" and adding the heated for extraction history), that would be enough for me to replace that injector. Maybe give Doktor A a call? Good luck. vic

[Boater]

I was told the other day by a specialist that if the ECU finds something wrong with the amount of leak off or blow by on an injector that it will or should shut the fuel off to stop the engine running.

I couldn't entirely fit this with my understanding of how black death occurs, or how few sensors my injection system has (my problem was a bit different in the end), but if you have a different spray pattern and leak off from one of your injectors it would definitely be worth having it reconditioned or replaced.

After my experience I am planning to use a bosch dealer to test and recondition my injectors because doubts have been planted about the independant I used - however no further comment on that until I have results from the bosch dealer, they may have done a proper job and it may simply be that I choose not to get all 5 rebuilt.

Jim

[tr4dude]

I just changed position in my company and will be one of two mechanics taking care of 20 rigs and 20 sprinters, all the sprinters have over 300k miles and several almost at 400k, i will be doing the rebuilds and from this experience I believe that every one that I build it will be a prerequisite that new injectors will be installed.

[Boater]

I don't know what the official MB line is, but my Haynes workshop manual reckons that injectors may need reconditioning as frequently as every 60000 miles to maintain full performance. I thought this sounded quite frequent, but it may be something to consider in your maintenance plan?